You don't have to look far to find folks who are freaked out by genetically modified foods, who won't drink cow's milk laced with growth hormones or touch diet colas sweetened with aspartame. Since we have so many hang-ups about the purity of what we eat and drink, you'd think that any company foolish enough to add substances whose quantity and quality are notoriously difficult to control to their snacks or beverages would quickly founder. Instead the exact opposite is true. In the U.S. last year, according to the market-research firm Frost and Sullivan, consumers bought $700 million of drinks spiked...